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Mike H...Steve Knight took off the corners of all his irons. IIRC, the intention was to reduce tracks, but all it did was turn a 2" iron into a 1-1/2" iron...it still left tracks unless you cambered the edge. A 2-3/4" wide plane with a 1-1/2" iron never made sense to me, but it was nearly effortless to push.
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Hi MikeI spent a while on Derek's site yesterday rereading various articles he has written on sharpening, especially since he started using CNC wheels. Like Derek I am largely a hand sharpener who likes to get done with the sharpening and back to cutting the wood. I was interested to read how Derek had evolved in his thinking about how much camber to put in a blade. From what I read I believe Derek himself is still working out precise cambers for specific planes and the blades they use.
I believe in cambering all blades for bench planes. Some context is required to understand some of the comments in my articles.
Firstly, the amount of camber will vary according to the type of plane. Smoothers get just enough camber to ensure that tracks are not left behind. Jointers get enough camber to enable one to correct out-of-square edges. Jacks and other coarse planes get the most camber so they can cut deeply and quickly.
The requirements for camber vary according to the width of the blade and whether the blade orientation is BU or BD (not a lot here, but just a little caused by geometry).
In every case there is no need to get fanatical. A little too much camber on a smoother will reduce the width of cut. So correct it next time. A shallower or deeper camber on a jack is the difference in efficiency, but may also be a decision based on then wood (some is more brittle).
When I wrote the article on the BU cambers, this was actually ground-breaking stuff at that time. It seems so obvious today, but at that time there was not an efficient method to camber BU blades, and so many just left them straight. The method (of a secondary microbevel on a low primary) was so novel that it became a topic presented at the WIA show that followed after. And yet I would go back now to those early articles and want to re-write them for clarity and perspective ... or just because I have better methods today. No time.
What I must do is correct a method for cambering a jack or scrub plane. I got away with it back then, but it is not recommended now. What I did was grind an 8" camber on a straight edge (using a template - the template is good. Keep this). What one should instead do is grind a flat (not bevelled) radius first, and then bevel it (today I do this on a 8" grinder. Many years ago I used a belt sander). Grinding the bevelled camber from the flat places the steel at risk for burning (I would do it slow and cool, but this does not come across). Grind the radius first, then add the bevel = less steel to remove = less heat.
This is wrong technique...
Instead, grind away the waste first to create the camber, and then bevel ...
Regards from Perth
Derek
Last edited by Derek Cohen; 10-23-2015 at 8:39 AM.
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Camber on a plane blade results in scalloped cuts. That is what you want for heavy stock removal, or should I say, you don't care if you get some scalloping because you will be cleaning it up anyway. Otherwise, the whole concept of camber is really hooey. You may want the edges of the blade slightly rounded so as not to dig in and leave tracks but otherwise there is no reason for camber. Take for example edge jointing. Why in the world would you strive to make a scalloped edge? You want that edge as straight and flat as possible. Take for example a tabletop which you expect to finish to a fine degree - you certainly don't want scalloping there, even if its a thou or two. Again, round over the very corners but give me a flat blade all day long.
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Hi Pat
The camber on a smoother is so slight that the surface left looks flat. Almost all of the camber is at the corners. The centre is almost flat. It it was actually flat (and you just rounded the corners) then you would be hard pressed to avoid some angling on the surface tops.
The camber when jointing edges is to enable you to "steer" the blade when jointing individual edges that are at different angles. If I was match planing, then I would use a flat blade. Again, the camber is very slight.
Regards from Perth
Derek
Last edited by Derek Cohen; 10-23-2015 at 8:33 AM.
Contributor
Interesting - yes, just round over the corners is what I'm saying - - you can call that a bit of camber on the corners if you wishOriginally Posted by Derek Cohen
Two questions for you though: "hard pressed to avoid some angling on the surface tops" - are you saying that you would tend to cause one side or the other of the blade to cut a bit deeper than the other without the camber?
Second question: "he camber when jointing edges is to enable you to "steer" the blade when jointing individual edges" - how do you mean steer the blade? somehow favoring one edge over the other? I'm having trouble picturing this
[OP]
Member
Hi Tom, yes I still have those two planes. I also find the reduced edges unnecessary, like you say reducing the angle on the corners but leaving the corners does much the same thing as 90% corners. I considered regrinding those blades now that I have CNC wheels. The reduced edge size, as you say, does make those blades slide nicely. I have quite a few 2" blades I got in my close out deal with Steve and a couple, almost 2" blades, made for HNT Gordon, that I picked up at Highland Woodworking on a close out sale. I probably will leave the blades on the planes Steve made close to how they are, just rounding the corners and adding a slight camber. Thanks for your thoughts/clarification on those blades.
Derek thanks very much for the update on your thoughts regarding grinding bevels. Derek's picture shows a stone wheel which I don't use these days. I use CNC wheels as I believe Derek typically does. I realize stones are more commonly used by a larger number of posters. I also know how people worry about over heating blades, including myself.
The first cambers I did followed Derek's current suggestions. I ground the radius then made my hollow bevel. Yesterday though, I tried just grinding the radius and hollow bevel at the same time. Like Derek mentions, at first my blade heated up due to the larger surface being ground even with a CNC wheel. Then I tried grinding both at the same time with light pressure against the wheel. I was very surprised to find out how large a difference the amount of pressure I made against the wheel translated into more heat. Once I eased off on the pressure against the wheel it seemed I could not make the blade heat up at all using a 180 CNC wheel. I make this point because I think my bad habit of pressing too hard against a stone grinder has caused me a large number of issues in the past, and still can when I forget. I believe I got into that habit trying to grind/regrind bevels on A2 BU plane blades on a Tormek. The Tormek was so slow it was hard to tell if it was working at all which caused me to use way too much pressure in an effort to make visible progress. I was making so much pressure I believe I was moving/bending the rod that holds jigs enough to throw things off. I was happy to discover that reducing the pressure against my wheel yesterday did not reduce how fast the wheel cut nearly as much as I thought it might. I have a SB (Stuart Beatty) angle setting jig that I use to set my SB tool rest's angle to the wheel. Oddly enough the 25 degree want touch the wheel due to the 65 setting hitting the wheel first, so I have been using the 30 mark/curve, which removes a little less metal. So far the greater angle has seemed to cut reasonably well.
In regard to major stock removal, I think a scalloped surface actually helps. The scallops obviously make an uneven surface but go deeper in the process. Removing the scallops is easy to do using a plane with a less dramatic camber. In regard to smoothing planes, I think we start getting into the question of which side of "perfectly straight" we want to have our error, knowing that there isn't actually any perfectly straight edge. I find slightly convex plane blades work better than slightly concave. We want a "flat" surface on the ends of dovetail tails too, but many people make them slightly concave as this error is preferable to slightly convex.
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Most of my planes have slight camber. For the 2" wide size- #4 & #5, I keep three or four blade/chipbreaker sets at various cambers. I have never measured radii of them, just if I need more camber than I have one set up for I'll grind a curvier one. Mostly if I'm doing scrub/fore/jack work I use the cambered blades in the #5 and leave the #4 set up as a smoother, but that isn't a rule or anything....
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On flatness/straightness of edges, and the rabbit hole that is sharpening.
I run a modifed Veritas Mk2 honing jig on very carefully and frequently flattened waterstones, and am confident in saying that the method if needed produces edges which if they are not dead straight are undetectably close to it. That's using the straight/cylindrical roller set up.
I switch to the camber roller (or even a narrow roller Eclipse type) on other jobs where less (or more in the case of the latter) camber is required.
One often overlooked advantage of the Veritas (or any other very wide roller) guide is that it has the potential to produce very straight edges. This because it creates a tipod/prevents the blade from tipping side to side. I can hand sharpen, but there are definite precision related advantages to using a jig...
Contributor
Wow am I missing something or is being way over thought?
To me its simple: ease the corners on my smoothers to eliminate tracks and keep a couple variably cambered blades around for quick stock removal.
I don't see the point in any camber at all on a smoothing plane unless you want to see tracks.
I keep a cambered blade for a 4 and a 6.
On the 6 I don't know what the radius is - its an arc but not as much as a scrubber.......what's the diff?
I just eyeball it when grinding but you can make a pattern.
Last edited by Robert Engel; 10-24-2015 at 7:32 AM.
Member
Is there any historical data that recommends you camber and/or ease the corners of your irons on all of your bench planes.
Stewie;
Member
Yes, Robert, you are missing something. For a smoother a rounded edge means the cut will feather to nothing at the edge. If you just round the corners, the edge of the cut is not as abrupt as a flat edge, but still noticeable nonetheless. Rounded tracks instead of square tracks. In addition the problems with having the iron slightly tilted to one side are much more severe with an iron that has rounded corners than one which has a nice sweeping curve. If you are not planing boards that are wider than the iron, it does not matter very much.
Last edited by Warren Mickley; 10-24-2015 at 8:13 AM.
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Warren described it well, better than I did. "Camber" on a smoother should not imply "rounded", since round leaves a scollop. The ends of the blade indeed "feather", which means they fade to nothing.
Regards from Perth
Derek
[OP]
Member
Yes, I think what Warren is saying is the crux of the situation here. There is some point at which, starting backwards with the smoothing plane, the blade curve becomes indistinguishable via the human eye. Like Warren says the "edge" made by the two corners of the blade start to fade away visually and even tactilely. It seems to me that approaching that curve on the edge of a smoothing plane is the ultimate in sharpening technique. It ultimately does not matter how sharp or straight a smoothers blade is if it leaves tracks does it? Sure maybe we can sand or scrape the tracks away but that is more steps and more work. Isn't one of our objectives to produce more interesting work than machines produce? Is a "perfectly' flat surface more interesting than one that hints at the techniques used to create it? As I know has been argued before, at what point does leveling of a surface go beyond utility and start becoming fruitless?
I have seen what I would term visually "perfect" surfaces made with very sharp drawknives. At least in my somewhat warped mind I do not think the surface made by a very sharp blade can be improved on. I am more interested in what the surface I make reveals in the wood visually. As I believe many on these pages have concluded over the years sanding or scraping ends up roughing the surface to obscure visual plane tracks. Do we want to leave a slightly rough surface and cover it with finish? Does this type finish obscure or embellish our work? Isn't that technique trying to copy what machines do? For me hand tool work is more "impressionistic" and should by definition impress via techniques that paint a broader less "perfect" picture. For me the beauty of work done with hand tools isn't in how close it comes to what a machine can do, it resides in the mystery and visual suspense it creates that can't be created with machines. Still we want our work to be at least as functional as machine made work so we do not want sharp edges or surfaces that are not at least as functional as machine made ones. Shouldn't we be attempting to do more than machines instead of following some misguided path that approaches but never quite achieves the more simplistic "perfect" work a machine does?
I learned some interesting things in Windsor Chair classes. Talented chair makers like Peter Galbert avoid sand paper and even scrapers, considering them indications that the drawknife and maybe spokeshave work were not done as well as they could have been. Galbert and his assistant seemed to feel that even picking up a spokeshave indicated that they may have made a stroke they had to correct with a "lesser" tool. They seemed to prefer to "paint" with a broader brush and longer strokes. I know that some of the more experienced hand plane people feel the same way about hand plane work. In chair making the objective isn't to make a "perfect" surface. Visually the maker wants the observer of the work to be able to tell that the work is not quite perfect, hand made. Isn't "perfect" a machine made characteristic that we should avoid instead of try to emulate?
Obviously, I still have more to learn from guys like Warren and Derek who are better at painting with broader strokes both with hand tools and words.
Last edited by Mike Holbrook; 10-24-2015 at 1:47 PM.
Member
Therefore, I sharpen more camber into a blade for a low angle bevel-up plane than for a bevel-down plane to achieve the same functional amount of camber. http://www.finewoodworking.com/item/...in-plane-irons
Member
Just as an aside, a historical detail.
In the 17th century the Dutch smoothing planes had a round corner on one side of the bottom of the plane, with a similar round corner grinded into the blade. It looks a bit like a rabbet plane with a round edge instead of a square one. The current idea is that the plane was used on the last passes over the wood, going in length wise strokes from right to left, thus eliminating the tracks from the square corner on the other side of the edge.
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